1. Field of the Invention
This invention relates to insulated glazing materials. More particularly, it relates to curved panel insulated glazing materials for use in architectural windows.
2. Description of Prior Art
In recent years, there has been increasing emphasis on the use of multipane insulating glazings in architectural structures. Government regulations have mandated the use of double- and triple-pane glazings. Energy costs have made the increased cost of these constructions a wise investment. Another trend in recent years has been an esthetic one. This has been the incorporation of curved window surfaces into building structures. Common applications for these curved structures have been greenhouse structures, arched entrances, and arched roofs over patios, walks, and the like. Very commonly, these curved panels make up a part of a large surface area glass structure. This makes it very important from an energy and comfort point of view to have the curved areas present multipane insulating properties. Without such properties, the heat loads presented can be huge. The conventional way to provide insulated windows has been to employ two or three parallel panes of glass, the faces of which are in spaced relationship, thereby providing between the glass panes one or two dead air spaces which impart insulating properties to the structure. In the most common arrangement, two parallel panes of glass are held in spaced relationship by metallic or plastic spacers or fasteners positioned around the perimeters of the panes. When a triple-pane glazing is desired, one approach has been to use three parallel sheets of glass. This structure can be extremely heavy.
Over the past few years, Southwall Technologies Inc., the assignee of the present invention, has promoted a triple-glazing structure which employs two glass panes with an intermediate plastic film. Such products are described, for example, in U.S. Pat. No. 4,335,166 of Lazardo et al. To achieve even better results, the internal plastic film can be coated with a heat-reflective layer, such as a dielectric/metal/dielectric interference filter of the general type described in U.S. Pat. No. 4,337,990 of Fan et al.
In these glass/plastic film/glass triple-pane structures, the plastic film is stretched taut. It is essential that there be no wrinkles or major discontinuities in the film. If such defects are present, the center film becomes an obtrusive interference in the window's visual properties. With flat-panel windows, a substantial body of technology has arisen to tension the internal film either by heat shrinking or by the use of mechanical tensioning devices. While these methods have proven suitable for flat panels, their use in curved panels has led to problems. For one, as the film is shrunk or tensioned in curved panels, using conventional flat-panel technology, in which the film is affixed to the full perimeter of the frame, the parallel relationship between the plastic film and the two glass panes is disturbed. This leads, at minimum, to visual distortion in the final product, and can in extreme cases lead to the film's contacting one of the glass panes so as to produce a major visual interruption.
It is the general object of this invention to provide an improved curved triple-glazing structure having as its middle glazing a plastic sheet. It is also an object of this invention to provide a method for producing such triple-pane glazings.